Modification of thiocolchicine following patterns established with colchicine, afforded analogs of thiocolchicine found highly potent in tubulin binding assays. In parallel reduced toxicity in mice and high potency in the P388 antitumor assay was detected with several analogs. Carbamates of deacetylthiocolchicines represent a novel group of potential antitumor and antigout compounds. Phenolic thiocolchicines and catecholic thiocolchicines were less potent in the tubulin binding assay. 1-Acetoxy- and 1,2-diacetoxy-analogs of thiocolchicine exist in solution as two isomers, possibly originating by atropisomerism. X- Ray diffraction of biologically potent and less potent colchicines was accomplished, showing little difference of the molecules in the solid state. Synthesis of thiodemecolcine and 3-demethyl-N-carbethoxydeacetylthiocolchicine was accomplished. Affinity labeling of colchicines by introducing spin-labels did not afford compounds useful for marking the colchicine binding site on tubulin. Esters of colchinoids with DADF were prepared, converted on tlc-plates after exposure to ammonia and iodine vapors into red colored and highly visible erythrosyl derivatives.